Apparatus and method for fabricating a light guiding grid

Abstract

A light guide grid can include a grid structure having a plurality of intersecting grid lines, each grid line having a width w, and a plurality of openings for photosensor elements between intersecting grid lines. The grid structure has a diagonal grid width between two adjacent ones of the plurality of openings in a diagonal direction. The diagonal grid width has a value exceeding approximately √3 w. An image sensor can include a light guide grid having a grid structure as described above and further include a micro-lens such as a sinking micro-lens and a color filter. A method of fabricating a light guide grid can include forming a grid above at least one photo sensor, the grid having intersecting grid lines of width w and a diagonal grid width in a diagonal direction having a value exceeding approximately √3 w.

We claim: 
     
       1. A light guide grid, comprising:
 a first grid structure having a plurality of intersecting first grid lines, each first grid line having a width w, and a plurality of first openings between the plurality of intersecting first grid lines; and 
 a second grid structure comprising a plurality of intersecting second grid lines disposed above a top surface of the intersecting first grid lines, the second grid structure further comprising a plurality of second openings between the plurality of intersecting second grid lines for a plurality of color filters placed between the intersecting first grid lines, wherein each of the color filters protrudes beyond a top surface of the intersecting second grid lines, 
 wherein each of the plurality of first openings are vertically offset from, have a different horizontal cross-sectional shape, and are larger than each of the second openings for the plurality of color filters, wherein each of the plurality of first openings is shaped to have straight side edges and rounded corners in which two side edges meet, the first grid structure having a diagonal grid width between two diagonally opposite rounded corners of two diagonally adjacent openings, and wherein the diagonal grid width is in the range of √3 w to 3 w. 
 
     
     
       2. The light guide grid of  claim 1 , wherein the width w has a value in a range from approximately 0.1 um to 1 um. 
     
     
       3. The light guide grid of  claim 1 , wherein the light guide grid is comprised of metal. 
     
     
       4. The light guide grid of  claim 1 , wherein the light guide grid is comprised of dielectric opaque materials. 
     
     
       5. The light guide grid of  claim 1 , wherein the diagonal grid width is greater than or equal to 2 w to reduce noise and crosstalk among photo sensor elements underneath. 
     
     
       6. The light guide grid of  claim 1 , wherein a lowest part of the second openings is higher than a lowest part of the first openings. 
     
     
       7. The light guide grid of  claim 1 , wherein the second openings comprise an octagonal horizontal cross-sectional shape. 
     
     
       8. An image sensor, comprising:
 a plurality of color filters; 
 a plurality of micro-lenses over the plurality of color filters, wherein the plurality of micro-lenses are abutting each other and are circle-shaped, and wherein each of the plurality of circle-shaped micro-lenses extends downwardly beneath a top surface of the plurality of color filters; and 
 a light guide grid, comprising:
 a first grid structure having a plurality of intersecting first grid lines, each first grid line having a width w, the first grid structure having a plurality of first openings placed between the plurality of intersecting first grid lines; and 
 a second grid structure comprising a plurality of intersecting second grid lines disposed above a top surface of the intersecting first grid lines, the second grid structure further comprising a plurality of second openings between the plurality of intersecting second grid lines for the plurality of color filters placed between the intersecting first grid lines, wherein each of the color filters protrudes beyond a top surface of the intersecting second grid lines, 
 
 wherein each of the plurality of first openings are vertically offset from, have a different horizontal cross-sectional shape, and are larger than each of the second openings for the plurality of color filters, wherein each of the plurality of first openings is shaped to have straight side edges and rounded corners in which two side edges meet, the first grid structure having a diagonal grid width between two diagonally opposite rounded corners of two diagonally adjacent openings, and wherein the diagonal grid width is in the range of √3 w to 3 w. 
 
     
     
       9. The image sensor of  claim 8 , wherein the diagonal grid width is greater than or equal to 2 w to reduce noise and crosstalk among photo sensor elements underneath. 
     
     
       10. The image sensor of  claim 8 , wherein the width w has a value in a range from approximately 0.1 um to 1 um. 
     
     
       11. The image sensor of  claim 8 , wherein the light guide grid is comprised of metal having a thickness of approximately 50 nm to 500 nm. 
     
     
       12. The image sensor of  claim 8 , wherein the light guide grid is comprised of dielectric materials. 
     
     
       13. An image sensor, comprising:
 a photo sensor element; 
 a plurality of color filters disposed over the photo sensor element; 
 a plurality of micro-lenses over the plurality of color filters, wherein the plurality of micro-lenses are abutting each other and are circle-shaped, and wherein each of the plurality of circle-shaped micro-lenses extends downwardly beneath a top surface of the plurality of color filters; and 
 a light guide grid, comprising:
 a first grid structure having a plurality of intersecting first grid lines, each first grid line having a width w, the first grid structure having a plurality of first openings placed between and the plurality of intersecting first grid lines; and 
 a second grid structure comprising a plurality of intersecting second grid lines disposed above a top surface of the intersecting first grid lines, the second grid structure further comprising a plurality of second openings between the plurality of intersecting second grid lines for the plurality of color filters placed between the intersecting first grid lines, wherein each of the color filters protrudes beyond a top surface of the intersecting second grid lines, 
 
 wherein each of the plurality of first openings are vertically offset from, have a different horizontal cross-sectional shape, and are larger than each of the second openings for the plurality of color filters, wherein each of the plurality of first openings is shaped to have straight side edges and rounded corners in which two side edges meet, the first grid structure having a diagonal grid width between two diagonally opposite rounded corners of two diagonally adjacent openings, and wherein the diagonal grid width is in the range of √3 w to 3 w. 
 
     
     
       14. The image sensor of  claim 13 , wherein the diagonal grid width is greater than or equal to 2 w. 
     
     
       15. The image sensor of  claim 13 , wherein the width w has a value in a range from approximately 0.1 um to 1 um. 
     
     
       16. The image sensor of  claim 13 , wherein the light guide grid is comprised of metal having a thickness of approximately 50 nm to 500 nm. 
     
     
       17. The image sensor of  claim 13 , wherein the light guide grid is comprised of dielectric materials. 
     
     
       18. The image sensor of  claim 13 , further comprising an anti-reflective coating (ARC) layer disposed between the photo sensor element and the color filter. 
     
     
       19. The image sensor of  claim 13 , further comprising a buffer layer disposed between the photo sensor element and the plurality of color filters. 
     
     
       20. The image sensor of  claim 13 , wherein the second openings are polygonal.